Poly[(μ₂-1,3-di-4-pyridylpropane-κ²N:N′)(μ₃-glutarato-κ³O:O′:O′′)dizinc(II)]

The title compound, [Zn₂(C₅H₆O₄)₂(C₁₃H₁₄N₂)]_n or [Zn₂(glu)₂(bpp)]_n, is a novel zinc polymer based on mixed flexible glutarate (glu) and 1,3-di-4-pyridylpropane (bpp) ligands. The Zn^II center has a distorted tetra­hedral geometry and the central atom of the bpp ligand is located at a special site with a C₂ axis passing through it. A layer is formed by Zn–glu bonding. Such layers are pillared by bpp ligands, forming a three-dimensional framework with large channels. The inverted inter­penetration of two three-dimensional frameworks completes the mol­ecular structure.

S1. Comment

Using versatile multidentate ligands to design metal-organic coordination polymers has mushroomed recently, not only because such ligands can construst intriguing structural topologies (Yaghi et al., 1998; Hagrman et al., 1999) but also because they have unexpected properties for potential application as functional materials (Piguet et al., 1997; Park et al., 2001). Some organic N-atom donors, such as bipyridines and their analogues, are often chosen to modify the structure and properties of these polymers (Davidson & Loeb, 2003; Biradha et al., 1999). In addition, long flexible multidentate ligands have shown the ability to produce unique interwoven extended structural motifs, such as polycatenanes (Carlucci et al., 2003), polyrotaxanes (Poleschak et al., 2004; Wang et al., 2004), double helices (Piguet et al., 1997) and other uncommon species (Carlucci, Ciani & Proserpio, 2004; Carlucci, Ciani, Proserpio & Spadacini, 2004). The 1,3-di-4-pyridylpropane (bpp) ligand, as an analogue of 4,4'-bipyridine, possesses variable flexibility and functionality owing to the introduction of three methylene groups between the two pyridyl rings (Mukherjee et al., 2003; Wen et al., 2005). The saturated aliphatic dicarboxylate ligands, which exhibit conformational and coordination versatility due to the presence of single-bonded carbon chains, are also an attractive choice and viewed as important flexible spacer ligands. As an elementary member of the α,ω-dicarboxylate family, the glutarato anion, C₅H₆O₄²⁻, has proven to be a versatile polydentate ligand (Zheng et al., 2004). However, metal coordination polymers based on mixed bpp and glutarate (glu) ligands, to our knowledge, have not been reported to date. In this paper, we report a novel Zn polymer, [Zn₂(glu)₂(bpp)]_n, (I), which features a three-dimensional architecture with interpenetration.

As shown in Fig. 1, the Zn^II center has a distorted tetrahedral geometry, which is defined by one of the pyridyl N atoms of the bpp ligand and three O atoms from three carboxylate groups of three different glu ligands. The Zn—N bond length is 2.039 (4) Å, and the Zn—O bond lengths fall in the range 1.935 (4)–1.991 (3) Å. The two carboxylate groups of the glu ligand have two coordination modes; the first bidentately bridges two Zn atoms in syn–syn fashion, the shortest Zn···Zn distance being 3.569 (1) Å, while another carboxylate group monodentately coordinates to the Zn atom. The shortest Zn···Zn distance between atoms separated by glu ligand is 8.786 (1) Å. The angle between the planes of two carboxylate groups is 77.02°. The twist in the glu ligand occurs at atom C3; the C1—C2—C3—C4 torsion angle is 71.2 (6)°. The bpp ligand acts as a µ₂-bridge and links two symmetry-related Zn centers with a Zn···Zn separation of 13.567 (2) Å. Atom C12 is located on a special site with a C₂ axis passing through it. The twist in the bpp ligand also occurs at atom C12; the C8—C11—C12—C11ⁱ [symmetry code: (i) −x, y, 1/2 − z] torsion angle is 174.5 (6) Å. The angle between the two pyridyl planes of the bpp ligand is 60.7°.

As shown in Fig. 2, the Zn atoms are interlinked by the glu ligands to generate a layer parallel to (111). The resulting layer is composed of 8- and 36-membered rings. It is interesting to note that no inversion center can be found in this layer. Such a layer can also be looked at as the vertical assembly of two groups of parallel chains with the di-metal units functioning as hinges. As shown in Fig. 3, the resulting layers are pillared by the flexible bpp ligands to form a three-dimensional open framework, which contains large channels along the b axis of dimensions 17.135 × 8.786 Å. Large channels can also be found along the a or c axis. Owing to the orderly connection of asymmetrical layers, there is no inversion center in a single open framework. The void spaces in the single framework are so large that two three-dimensional frameworks can interpenetrate each other, so as to complete the final three-dimensional architecture (Fig. 4). An inversion center exists between the two independent frameworks owing to their inverted interpenetration.

In summary, we have successfully synthesized and structurally characterized a novel Zn polymer based on mixed flexible glu and bpp ligands. It is the first example of a coordination polymer composed of two such long flexible ligands.

S2. Experimental

A mixture of ZnCl₂ (0.13 g, 1.0 mmol) with glutarate acid (0.13 g, 1.0 mmol), bpp (0.10 g, 0.5 mmol) and NaOH (0.04 g, 1 mmol) in the molar ratio 2:2:1:2 and water (20 ml) was placed in a Parr Teflon-lined stainless steel vessel (25 ml); the vessel was sealed and heated to 433 K for 3 d, and the reactant was cooled at a rate of 0.3 K min⁻¹ to lead to the formation of colorless (I) with yield of 53% based on bpp. Analysis calculated for C₂₃H₂₆N₂O₈Zn₂: C, 46.88.10; H, 4.45; N, 4.75. Found: C, 47.00; H, 4.76; N, 4.64%. IR (solid KBr pellet, v/cm⁻¹): 1611 (versus), 1570 (s), 1383 (s), 1294 (w), 1215 (m), 1085 (w), 1017 (w), 817 (m), 635 (m), 495 (w).

S3. Refinement

The H atoms bonded to C atoms were positioned geometrically and refined using a riding model [C—H_aromatic 0.93 Å and C—H_aliphatic = 0.97 Å, U_iso(H) = 1.2U_eq(C)].

Computing details

Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2002); software used to prepare material for publication: SHELXL97.

Figures

	Fig. 1. A view of (I), with 30% probability displacement ellipsoids; H atoms have been omitted. [Symmetry codes: (A) 1/2 + x, −1/2 + y, z; (B) −1/2 − x, −1/2 + y, −1/2 − z; (C) −x, y, −1/2 − z; (D) −x, y, 1/2 − z; (E) −1/2 + x, 1/2 + y, z; (F) −1/2 − x, 1/2 + y, −1/2 − z.]
	Fig. 2. The layered structure in (I), showing Zn atoms bridged by glu ligands.
	Fig. 3. Topology of the structure of complex (I), showing layers being pillared by the flexible bpp ligands and the formation of large channels.
	Fig. 4. The inverted interpenetration framework of (I).

Poly[(µ₃glutarato-κ³O:O':O'')(µ₂-1,3-di-4-pyridylpropane- κ²N:N')dizinc(II)]

Crystal data

[Zn2(C5H6O4)2(C13H14N2)]	F(000) = 1208
Mr = 589.24	Dx = 1.607 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 1769 reflections
a = 10.5886 (15) Å	θ = 2.5–25.1°
b = 14.0238 (19) Å	µ = 2.02 mm^−1
c = 17.135 (2) Å	T = 293 K
β = 106.838 (2)°	Prism, colorless
V = 2435.3 (6) Å^3	0.15 × 0.10 × 0.08 mm
Z = 4

Data collection

Bruker SMART CCD area-detector diffractometer	2158 independent reflections
Radiation source: fine-focus sealed tube	1619 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.032
π and ω scans	θmax = 25.1°, θmin = 2.5°
Absorption correction: empirical (using intensity measurements) (SADABS; Sheldrick, 1996)	h = −10→12
Tmin = 0.785, Tmax = 0.851	k = −12→16
3817 measured reflections	l = −20→20

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.130	H-atom parameters constrained
S = 1.05	w = 1/[σ^2(Fo^2) + (0.061P)^2 + 8.7107P] where P = (Fo^2 + 2Fc^2)/3
2158 reflections	(Δ/σ)max = 0.001
159 parameters	Δρmax = 0.52 e Å^−3
0 restraints	Δρmin = −0.78 e Å^−3

Special details

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F² against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F², conventional R-factors R are based on F, with F set to zero for negative F². The threshold expression of F² > σ(F²) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F² are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Zn1	0.00251 (5)	0.25747 (4)	−0.14543 (3)	0.0326 (2)
O1	0.0732 (3)	0.3855 (2)	−0.1373 (2)	0.0467 (9)
O2	−0.1140 (4)	0.4060 (3)	−0.1111 (3)	0.0552 (11)
O3	−0.3333 (4)	0.7122 (3)	−0.2865 (2)	0.0507 (10)
O4	−0.3454 (3)	0.6850 (3)	−0.1617 (2)	0.0427 (9)
N1	0.0017 (4)	0.1888 (3)	−0.0407 (2)	0.0323 (9)
C1	−0.0110 (5)	0.4383 (3)	−0.1180 (3)	0.0328 (11)
C2	0.0286 (5)	0.5415 (3)	−0.0999 (3)	0.0380 (12)
H2A	0.0800	0.5616	−0.1355	0.046*
H2B	0.0847	0.5463	−0.0442	0.046*
C3	−0.0879 (5)	0.6091 (4)	−0.1110 (3)	0.0405 (13)
H3A	−0.1467	0.5839	−0.0818	0.049*
H3B	−0.0557	0.6704	−0.0872	0.049*
C4	−0.1641 (5)	0.6231 (4)	−0.1994 (3)	0.0413 (13)
H4A	−0.1069	0.6549	−0.2262	0.050*
H4B	−0.1844	0.5606	−0.2242	0.050*
C5	−0.2906 (5)	0.6786 (3)	−0.2170 (3)	0.0314 (11)
C6	−0.1113 (5)	0.1770 (4)	−0.0214 (3)	0.0413 (13)
H6	−0.1887	0.2018	−0.0562	0.050*
C7	−0.1174 (5)	0.1298 (4)	0.0477 (3)	0.0457 (14)
H7	−0.1980	0.1233	0.0587	0.055*
C8	−0.0047 (5)	0.0920 (3)	0.1009 (3)	0.0363 (12)
C9	0.1119 (5)	0.1057 (4)	0.0816 (3)	0.0408 (13)
H9	0.1909	0.0831	0.1163	0.049*
C10	0.1108 (5)	0.1528 (4)	0.0112 (3)	0.0383 (12)
H10	0.1903	0.1600	−0.0010	0.046*
C11	−0.0087 (6)	0.0381 (4)	0.1760 (3)	0.0484 (14)
H11A	0.0639	−0.0070	0.1898	0.058*
H11B	−0.0901	0.0018	0.1636	0.058*
C12	0.0000	0.1003 (5)	0.2500	0.0421 (18)
H12A	0.0773	0.1409	0.2606	0.051*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Zn1	0.0316 (3)	0.0381 (4)	0.0286 (3)	−0.0018 (3)	0.0095 (2)	−0.0053 (3)
O1	0.037 (2)	0.036 (2)	0.071 (3)	0.0045 (17)	0.0215 (19)	−0.0082 (18)
O2	0.046 (2)	0.047 (2)	0.080 (3)	−0.0070 (19)	0.031 (2)	−0.004 (2)
O3	0.039 (2)	0.077 (3)	0.034 (2)	0.019 (2)	0.0069 (16)	0.021 (2)
O4	0.046 (2)	0.047 (2)	0.040 (2)	0.0137 (17)	0.0195 (17)	0.0033 (17)
N1	0.032 (2)	0.039 (2)	0.027 (2)	0.0042 (18)	0.0091 (17)	−0.0023 (18)
C1	0.031 (3)	0.033 (3)	0.031 (3)	0.005 (2)	0.005 (2)	0.001 (2)
C2	0.034 (3)	0.035 (3)	0.042 (3)	−0.001 (2)	0.006 (2)	0.000 (2)
C3	0.048 (3)	0.032 (3)	0.036 (3)	0.010 (2)	0.004 (2)	−0.004 (2)
C4	0.045 (3)	0.047 (3)	0.032 (3)	0.013 (3)	0.013 (2)	0.002 (2)
C5	0.030 (2)	0.032 (3)	0.033 (3)	0.000 (2)	0.011 (2)	−0.001 (2)
C6	0.028 (3)	0.056 (3)	0.036 (3)	0.008 (2)	0.004 (2)	0.000 (3)
C7	0.040 (3)	0.063 (4)	0.039 (3)	−0.004 (3)	0.020 (2)	0.001 (3)
C8	0.043 (3)	0.034 (3)	0.031 (3)	−0.002 (2)	0.008 (2)	−0.005 (2)
C9	0.030 (3)	0.050 (3)	0.038 (3)	0.008 (2)	0.005 (2)	0.000 (3)
C10	0.030 (3)	0.050 (3)	0.036 (3)	0.003 (2)	0.011 (2)	0.000 (2)
C11	0.072 (4)	0.037 (3)	0.041 (3)	−0.007 (3)	0.024 (3)	−0.003 (3)
C12	0.057 (5)	0.042 (4)	0.028 (4)	0.000	0.014 (3)	0.000

Geometric parameters (Å, º)

Zn1—O1	1.935 (4)	C3—H3A	0.9700
Zn1—O3^i	1.940 (3)	C3—H3B	0.9700
Zn1—O4^ii	1.991 (3)	C4—C5	1.502 (7)
Zn1—N1	2.039 (4)	C4—H4A	0.9700
Zn1—O2	2.574 (4)	C4—H4B	0.9700
Zn1—C1	2.591 (5)	C6—C7	1.374 (7)
O1—C1	1.275 (6)	C6—H6	0.9300
O2—C1	1.218 (6)	C7—C8	1.381 (7)
O3—C5	1.238 (6)	C7—H7	0.9300
O3—Zn1^iii	1.940 (3)	C8—C9	1.381 (7)
O4—C5	1.248 (6)	C8—C11	1.504 (7)
O4—Zn1^iv	1.991 (3)	C9—C10	1.372 (7)
N1—C6	1.341 (6)	C9—H9	0.9300
N1—C10	1.336 (6)	C10—H10	0.9300
C1—C2	1.513 (7)	C11—C12	1.520 (7)
C2—C3	1.523 (7)	C11—H11A	0.9700
C2—H2A	0.9700	C11—H11B	0.9700
C2—H2B	0.9700	C12—C11^v	1.520 (7)
C3—C4	1.509 (7)	C12—H12A	0.9700
O1—Zn1—O3^i	128.16 (17)	C4—C3—H3B	109.1
O1—Zn1—O4^ii	99.88 (14)	C2—C3—H3B	109.1
O3^i—Zn1—O4^ii	113.10 (16)	H3A—C3—H3B	107.8
O1—Zn1—N1	118.37 (17)	C5—C4—C3	117.1 (4)
O3^i—Zn1—N1	97.82 (16)	C5—C4—H4A	108.0
O4^ii—Zn1—N1	95.28 (15)	C3—C4—H4A	108.0
O1—Zn1—O2	55.52 (13)	C5—C4—H4B	108.0
O3^i—Zn1—O2	88.98 (15)	C3—C4—H4B	108.0
O4^ii—Zn1—O2	154.89 (14)	H4A—C4—H4B	107.3
N1—Zn1—O2	93.24 (14)	O3—C5—O4	125.6 (4)
O1—Zn1—C1	28.25 (15)	O3—C5—C4	116.5 (4)
O3^i—Zn1—C1	109.85 (17)	O4—C5—C4	117.9 (4)
O4^ii—Zn1—C1	127.90 (15)	N1—C6—C7	122.7 (5)
N1—Zn1—C1	106.76 (16)	N1—C6—H6	118.7
O2—Zn1—C1	27.28 (13)	C7—C6—H6	118.7
C1—O1—Zn1	105.8 (3)	C8—C7—C6	120.4 (5)
C1—O2—Zn1	77.1 (3)	C8—C7—H7	119.8
C5—O3—Zn1^iii	136.0 (3)	C6—C7—H7	119.8
C5—O4—Zn1^iv	135.7 (3)	C7—C8—C9	116.8 (5)
C6—N1—C10	116.8 (4)	C7—C8—C11	121.7 (5)
C6—N1—Zn1	120.4 (3)	C9—C8—C11	121.6 (5)
C10—N1—Zn1	122.8 (3)	C10—C9—C8	119.8 (5)
O2—C1—O1	121.5 (5)	C10—C9—H9	120.1
O2—C1—C2	122.6 (5)	C8—C9—H9	120.1
O1—C1—C2	115.9 (4)	N1—C10—C9	123.5 (5)
O2—C1—Zn1	75.6 (3)	N1—C10—H10	118.2
O1—C1—Zn1	45.9 (2)	C9—C10—H10	118.2
C2—C1—Zn1	161.2 (3)	C8—C11—C12	114.5 (4)
C1—C2—C3	113.8 (4)	C8—C11—H11A	108.6
C1—C2—H2A	108.8	C12—C11—H11A	108.6
C3—C2—H2A	108.8	C8—C11—H11B	108.6
C1—C2—H2B	108.8	C12—C11—H11B	108.6
C3—C2—H2B	108.8	H11A—C11—H11B	107.6
H2A—C2—H2B	107.7	C11—C12—C11^v	109.9 (6)
C4—C3—C2	112.6 (4)	C11—C12—H12A	109.7
C4—C3—H3A	109.1	C11^v—C12—H12A	109.7
C2—C3—H3A	109.1

Symmetry codes: (i) −x−1/2, y−1/2, −z−1/2; (ii) x+1/2, y−1/2, z; (iii) −x−1/2, y+1/2, −z−1/2; (iv) x−1/2, y+1/2, z; (v) −x, y, −z+1/2.